There are numerous publications in the patent literature which disclose polyester amine dispersants derived from a poly(C2-4-alkylene imine) (hereinafter PAI) such as polyethylene imine (hereinafter PEI) to which is attached a polyester chain. The polyester chain may be derived from 12-hydroxy stearic acid as disclosed in U.S. Pat. No. 4,224,212 or it may be derived from two or more different hydroxy carboxylic acids or lactones thereof as disclosed in U.S. Pat. No. 5,700,395 and U.S. Pat. No. 6,197,877. It has now been found that still further improvements may be made whereby any amino and/or imino groups in the polyalkylene imine are reacted with either oxygen or urea. Improvements include at least one of superior fluidity of pigment dispersions; use in acid catalysed, epoxy and isocyanate coating processes; and resistant to discoloration when exposed to UV light.